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 Robotics / RCX / 2278
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Subject: 
Re: multiple motors
Newsgroups: 
lugnet.robotics.rcx
Date: 
Tue, 25 Nov 2003 14:12:55 GMT
Viewed: 
3663 times
  
In lugnet.robotics.rcx, Steve Hassenplug wrote:
In lugnet.robotics.rcx, Brian Davis wrote:
and the remaining two motors (one left & one right) from OUT_B.
All's well and good when running forward or backward, but to turn I'm in
trouble: the last two motors will try to fight each other. Obviously I don't
power OUT_B during a turn, but if OUT_B is set to Float those last two
   B) Is there a better way to do this? Run six motors in two triplets from

Well, I've never actually tried running six motors directly from the RCX.
However, I have used three motors to drive a sumo robot.

And I've also used four motors (two on each side) to drive six wheels (two on
the right, two on the left, and two in the middle)

The key is to use a differential.

With six motors (double what I did with three), put two motors on each side
(2xRight + 2xLeft), and the other two are connected to a differential, in the
middle (like the drive wheels in a car).  They will suppily power to both sides.
When the robot is going forward/reverse you can drive all motors.  When the
robot is turning, you can float or brake the middle motors, like you've been
doing.

The only hard part is making sure all your gear ratios are the same.

I'm just thinking out loud here, but it seems that the problem with the two
middle motors is that they are wired together.  So even if the RCX is told to
float the motor output, both motors will want to turn together.  If one turns,
it will act as a generator to turn the other.  I'm not sure if the differential
will solve this problem, because you are still relying on the two motors
spinning different amounts or in different directions.  (But again, I'm thinking
out loud and don't really know whether this is the case.)

And my BIGGEST piece of advice for your sumo robot: make SURE it
does not leave the sumo area on it's own.

Right.  At least make sure it takes the other robot with it...

- Chris.



Message has 1 Reply:
  Re: multiple motors
 
(...) Yes, that was the problem Brian was having. And, because the LEGO motors are so efficent, they work really well as generators. So, if you hook two together, and try to turn 1 and stop the other, you will have problems. I'm not sure I explained (...) (21 years ago, 25-Nov-03, to lugnet.robotics.rcx)

Message is in Reply To:
  Re: multiple motors
 
(...) Well, I've never actually tried running six motors directly from the RCX. However, I have used three motors to drive a sumo robot. And I've also used four motors (two on each side) to drive six wheels (two on the right, two on the left, and (...) (21 years ago, 25-Nov-03, to lugnet.robotics.rcx)

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